Thin film magnetic head and method of manufacturing the same

ABSTRACT

Provided is a thin film magnetic head capable of inhibiting the occurrence of track erasing and improving the reliability of magnetic recording. Two taper surfaces are disposed on both sides of a return yoke layer. As no corner portion which may induce concentration of a magnetic flux exists on the both sides of the return yoke layer, even if the magnetic flux emitted from a pole layer is returned to the return yoke layer through a hard disk, a magnetic field strength is not locally and pronouncedly concentrated in proximity to the taper surfaces of the return yoke layer. Thereby, the concentration of the magnetic flux can be prevented, and the probability of the occurrence of unnecessary recording decreases, so the occurrence of track erasing can be inhibited, and the reliability of magnetic recording can be improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a thin film magnetic headmagnetically recording by use of, for example, a perpendicular recordingsystem, and a method of manufacturing the same.

[0003] 2. Description of the Related Art

[0004] In recent years, magnetic recording apparatuses such as, forexample, hard disk drives which record information on hard disks havebeen in widespread use as information recording sources. In thedevelopment of hard disk drives, an improvement in performance of thinfilm magnetic heads has been sought in accordance with an increase inthe areal density of the hard disks. As magnetic recording systemsapplicable to thin film magnetic heads, for example, a longitudinalrecording system that a signal magnetic field is oriented in an in-planedirection (a longitudinal direction) of a hard disk and a perpendicularrecording system that the signal magnetic field is oriented in adirection perpendicular to a surface of the hard disk are well known. Atpresent, the longitudinal recording system is widely used, but inconsideration of market forces in accordance with an improvement inareal density, the perpendicular recording system instead of thelongitudinal recording system holds promise for future, because theperpendicular recording system can obtain an advantage that higher linerrecording density can be achieved, and a recording medium in which datahas been already recorded has resistance to thermal decay effects.

[0005] As recording modes using the perpendicular recording system, forexample, a mode in which recording on a single layer hard disk isperformed by a main part through using a head (ring type head) facingeach other with a gap in between on a side of an end and beingmagnetically coupled to each other on a side of the other end, or a modein which recording on a two-layer hard disk is performed by a main partthrough using a head (single-pole type head) being disposedperpendicular to the hard disk has been proposed. In these modes, basedupon a point that the mode using a combination of the single-pole typehead and the two-layer hard disk has superior resistance to thermaldecay, the mode becomes a focus of attention as a mode which can improvethe performance of thin film magnetic heads.

[0006] The perpendicular recording system thin film magnetic headcomprises a single-pole type head and a thin film coil generating amagnetic flux. The single-pole type head includes a pole layer emittingthe magnetic flux generated by the thin film coil toward the hard disk,and a return magnetic layer where the magnetic flux emitted from thepole layer to magnetize the hard disk is returned, and an end surface ofthe pole layer and an end surface of the return magnetic layer areexposed to an air bearing surface (recording-medium-facing surface)facing the hard disk. The return magnetic layer is magnetically coupledto the pole layer, for example, on a side away from the air bearingsurface, and is generally called “return yoke”.

[0007] In the perpendicular recording system thin film magnetic head, ina state in which the single-pole type head faces the hard disk, when themagnetic flux generated by the thin film coil is emitted from the polelayer toward the hard disk, the magnetic flux is returned to the returnmagnetic layer through the hard disk. At this time, a perpendicularmagnetic field for recording is generated by the magnetic flux emittedfrom the pole layer, and the perpendicular magnetic field magnetizes thehard disk so as to record information on the hard disk.

[0008] In order to improve recording performance of the perpendicularrecording system thin film magnetic head, for example, it is required toinhibit an influence of a problem called “track erasing” as much aspossible. Track erasing mainly means a phenomenon in which duringrecording to a target track on the hard disk, information recorded onother tracks except for the target track is erased without intention.When track erasing occurs, information cannot be stably recorded on thehard disk, so the reliability of magnetic recording decreases.

[0009] However, in a conventional perpendicular recording system thinfilm magnetic head, measures to inhibit the occurrence of track erasingmainly resulting from a returning mechanism of the magnetic flux duringrecording is not sufficient yet.

SUMMARY OF THE INVENTION

[0010] In view of the foregoing, it is an object of the invention toprovide a thin film magnetic head capable of inhibiting the occurrenceof track erasing and improving the reliability of magnetic recording.

[0011] A thin film magnetic head according to the invention comprises athin film coil generating a magnetic flux, a pole layer having a poleend surface exposed to a recording-medium-facing surface facing arecording medium, and emitting the magnetic flux generated by the thinfilm coil from the pole end surface toward the recording medium, and areturn magnetic layer where the magnetic flux emitted from the polelayer to magnetize the recording medium is returned, wherein the returnmagnetic layer includes an end surface exposed to therecording-medium-facing surface and a width change portion with a widthcontinuously narrowed toward the end surface.

[0012] In the thin film magnetic head according to the invention, thereturn magnetic layer includes a width change portion with a widthcontinuously narrowed toward the end surface exposed to therecording-medium-facing surface, and includes no corner portion in awidth direction in proximity to the recording-medium-facing surface, solocal concentration of the returned magnetic flux resulting from theexistence of the corner portion can be prevented.

[0013] In a method of manufacturing a thin film magnetic head accordingto the invention, the thin film magnetic head comprises a thin film coilgenerating a magnetic flux, a pole layer having a pole end surfaceexposed to a recording-medium-facing surface facing a recording mediumand emitting the magnetic flux generated by the thin film coil from thepole end surface toward the recording medium, and a return magneticlayer where the magnetic flux emitted from the pole layer to magnetizethe recording medium is returned, and the method comprises the steps offorming a precursor return magnetic layer as a preparatory layer of thereturn magnetic layer so as to include a precursor width change portionwith a continuously narrowed width, and polishing a laminate includingthe precursor return magnetic layer until reaching a halfway point ofthe precursor width change portion so as to form therecording-medium-facing surface, thereby forming the return magneticlayer so as to have an end surface exposed to therecording-medium-facing surface and include a width change portion witha width continuously narrowed toward the end surface.

[0014] In the method of manufacturing the thin film magnetic headaccording to the invention, after a precursor return magnetic layer as apreparatory layer of the return magnetic layer is formed so as toinclude a precursor width change portion with a continuously narrowedwidth, the precursor return magnetic layer is polished at least untilreaching a halfway point of the precursor width change portion so as toform the recording-medium-facing surface, thereby the return magneticlayer is formed so as to have an end surface exposed to therecording-medium-facing surface and include a width change portion witha width continuously narrowed toward the end surface.

[0015] In the thin film magnetic head according to the invention, thewidth of the width change portion is preferably narrowed from bothsides. In this case, it is preferable that the width change portion hastaper surfaces on both sides, and an angle between each of the tapersurfaces and the recording-medium-facing surface is within a range from5° to 40°.

[0016] Moreover, the thin film magnetic head according to the inventionmay further comprise a first shield layer magnetically shielding thepole layer from its surroundings, wherein the first shield layerincludes a portion with a width continuously narrowed from apredetermined position on a side away from the recording-medium-facingsurface toward recording-medium-facing surface.

[0017] The thin film magnetic head according to the invention mayfurther comprise a magnetoresistive device and a second shield layermagnetically shielding the magnetoresistive device from itssurroundings, wherein the second shield layer includes a portion with awidth continuously narrowed from a predetermined position on a side awayfrom the recording-medium-facing surface toward therecording-medium-facing surface.

[0018] Further, in the thin film magnetic head according to theinvention, the pole layer may emit a magnetic flux for magnetizing therecording medium in a direction perpendicular to a surface of therecording medium.

[0019] Other and further objects, features and advantages of theinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIGS. 1A and 1B are sectional views of a thin film magnetic headaccording to an embodiment of the invention;

[0021]FIG. 2 is a enlarged perspective view of a main part of the thinfilm magnetic head shown in FIGS. 1A and 1B;

[0022]FIG. 3 is an enlarged plan view of the main part of the thin filmmagnetic head shown in FIGS. 1A and 1B;

[0023]FIG. 4 is an illustration for describing the flow of a magneticflux during recording by the thin film magnetic head according to theembodiment of the invention;

[0024]FIG. 5 is an illustration for describing the flow of a magneticflux during recording by a conventional thin film magnetic head;

[0025]FIG. 6 is an illustration schematically showing results ofmeasurement relating to a correlation between the shape of a return yokelayer and the magnetic field strength;

[0026]FIG. 7 is a graph showing a taper angle dependence of a ratio ofthe magnetic field strength;

[0027]FIG. 8 is a plan view of a modification of the thin film magnetichead according to the embodiment of the invention;

[0028]FIG. 9 is a plan view of another modification of the thin filmmagnetic head according to the embodiment of the invention;

[0029]FIGS. 10A and 10B are sectional views for describing one step in amethod of manufacturing the thin film magnetic head according to theembodiment of the invention;

[0030]FIGS. 11A and 11B are sectional views for describing a stepfollowing the step of FIGS. 10A and 10B;

[0031]FIGS. 12A and 12B are sectional views for describing a stepfollowing the step of FIGS. 11A and 11B;

[0032]FIGS. 13A and 13B are sectional views for describing a stepfollowing the step of FIGS. 12A and 12B;

[0033]FIG. 14 is a plan view corresponding to the sectional views shownin FIGS. 10A and 10B;

[0034]FIG. 15 is a plan view corresponding to the sectional views shownin FIGS. 11A and 11B; and

[0035]FIG. 16 is a plan view corresponding to the sectional views shownin FIGS. 12A and 12B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Preferred embodiments of the invention will be described in moredetail below referring to the accompanying drawings.

[0037] At first, referring to FIGS. 1A and 1B, the structure of a thinfilm magnetic head according to an embodiment of the invention will bedescribed below. FIGS. 1A and 1B show sectional views of the thin filmmagnetic head, and FIG. 1A shows a sectional view parallel to an airbearing surface, and FIG. 1B shows a sectional view perpendicular to theair bearing surface.

[0038] In the following description, a distance in an X-axis direction,a distance in a Y-axis direction and a distance in a Z-axis direction inFIGS. 1A and 1B are expressed as “a width”, “a length” and “athickness”, respectively. Further a side closer to an air bearingsurface in the Y-axis direction is expressed as “front or frontward”,and the opposite side is expressed as “rear or rearward”. In FIGS. 2through 16, these directions are expressed as the same.

[0039] The thin film magnetic head according to the embodiment ismounted in, for example, a magnetic recording apparatus such as a harddisk drive or the like as a device for magnetic recording. The thin filmmagnetic head is, for example, a composite head capable of implementingtwo functions of recording and reproducing, and as shown in FIGS. 1A and1B, the thin film magnetic head comprises an insulating layer 2 made of,for example, aluminum oxide (Al₂O₃; hereinafter simply referred to as“alumina”), a reproducing head portion 100A using a magnetoresistive(MR) effect to perform reproducing, a recording head portion 100Bperforming recording by a perpendicular recording system and an overcoatlayer 14 made of, for example, alumina or the like laminated in thisorder on a substrate 1 made of, for example, a ceramic material such asAlTiC (Al₂O₃.TiC).

[0040] The reproducing head portion 100A comprises, for example, abottom shield layer 3, a shield gap film 4 and a top shieldlayer-cum-return yoke layer (hereinafter simply referred to as “returnyoke layer) 6 laminated in this order. An MR device 5 as a magneticreproducing device is buried in the shield gap film 4 so that a surfaceof the MR device 6 is exposed to an air bearing surface 20.

[0041] Mainly, the bottom shield layer 3 and the return yoke layer 6 areprovided to magnetically shield the MR device 5 from its surroundings.The bottom shield layer 3 and the return yoke layer 6 are made of, forexample, a magnetic material such as a nickel iron alloy (NiFe;hereinafter simply referred to as “Permalloy (trade name)”; Ni: 80 wt %,Fe: 20 wt %) with a thickness of approximately 1.0 μm to 2.0 μm.

[0042] The shield gap film 4 is provided to magnetically andelectrically separate the MR device 5 from the bottom shield layer 3 andthe return yoke layer 6. The shield gap film 4 is made of, for example,a non-magnetic and non-conductive material such as alumina with athickness of approximately 0.1 μm to 0.2 μm.

[0043] The MR device 5 uses, for example, a giant magnetoresistive (GMR)effect or a tunneling magnetoresistive (TMR) effect to performreproducing. Herein, the MR device 5 corresponds to a specific exampleof “a magnetoresistive device” in the invention.

[0044] The recording head portion 100B comprises, for example, a returnyoke layer 6, a gap layer 7 and a yoke layer 9 in which a thin film coil8 is buried, a pole layer 11 magnetically coupled to the return yokelayer 6 through an aperture 7K disposed in the gap layer 7 and the yokelayer 9, an insulating layer 12 and a write shield layer 13 laminated inthis order.

[0045] As described above, the return yoke layer 6 has a function ofmagnetically shielding the MR device 5 from its surrounding in thereproducing head portion 10A, and a function of returning a magneticflux emitted from the pole layer 11 through a hard disk (not shown) inthe recording head portion 100B. The return yoke layer 6 is made of, forexample, a magnetic material such as Permalloy (Ni: 80 wt %, Fe: 20 wt%) or the like with a thickness of approximately 1.0 μm to 4.0 μm.Herein, the return yoke layer 6 corresponds to a specific example of “areturn magnetic layer” in the invention.

[0046] The gap layer 7 includes a gap layer portion 7A disposed on thereturn yoke layer 6 and having the aperture 7K, a gap layer portion 7Bdisposed on the gap layer portion 7A so that gaps between windings ofthe thin film coil 8 and their surroundings are coated with the gaplayer portion 7B, and a gap layer portion 7C disposed so that the gaplayer portions 7A and 7B are partially coated with the gap layer portion7C.

[0047] The gap layer portion 7A is made of, for example, a non-magneticand non-conductive material such as alumina or the like with a thicknessof approximately 0.1 μm to 1.0 μm. The gap layer portion 7B is made of,for example, a photoresist (photosensitive resin) exhibiting liquidityby heating, a spin-on glass (SOG) exhibiting liquidity by heating or thelike. The gap layer portion 7C is made of, for example, a non-magneticand nonconductive material such as alumina, silicon oxide (SiO₂) or thelike with a larger thickness than that of the gap layer portion 7B.

[0048] The thin film coil 8 is provided mainly to generate a magneticflux for recording. The thin film coil 8 is made of, for example, ahigh-conductive material such as copper (Cu) or the like, and has awinding structure in a spiral shape while regarding a coupling portionbetween the return yoke layer 6 and the yoke layer 9 as a center. InFIGS. 1A and 1B, only a part of a plurality of windings constituting thethin film coil 8 is shown.

[0049] The yoke layer 9 is provided to magnetically couple the returnyoke layer 6 to the pole layer 11, and is made of, for example, amagnetic material such as Permalloy (Ni: 80 wt %, Fe: 20 wt %) or thelike. For example, the position of a surface of the yoke layer 9 in athickness direction coincides with the position of a surface of the gaplayer portion 7C in the same direction, that is, the surfaces of theyoke layer 9 and the gap layer portion 7C constitute a flat surface M.

[0050] The pole layer 11 is provided mainly to contain the magnetic fluxgenerated by the thin film coil 8 and emit the magnetic flux toward thehard disk (not shown). The pole layer 11 is made of, for example, aniron cobalt alloy (FeCo), an iron-based alloy (Fe—M; M represents ametal element selected from Groups 4A, 5A, 6A, 3B and 4B), a nitride ofany of these alloys, or the like with a thickness of approximately 0.1μm to 0.5 μm.

[0051] Mainly, the insulating layer 12 is provided to magnetically andelectrically separate the pole layer 11 from the write shield layer 13,and is made of, for example, a non-magnetic and non-conductive materialsuch as alumina or the like.

[0052] Mainly, the write shield layer 13 is provided to magneticallyshield the pole layer 11 from its surroundings. The write shield layer13 is made of, for example, a magnetic material such as Permalloy (Ni:80 wt %, Fe: 20 wt %) with a thickness of approximately 1.0 μm to 2.0μm. Herein, the write shield layer 13 corresponds to a specific exampleof “a first shield layer” in the invention.

[0053] Next, referring to FIGS. 2 and 3, the structure of a main part ofthe thin film magnetic head will be described in more detail below. FIG.2 shows an enlarged perspective view of the main part of the thin filmmagnetic head shown in FIGS. 1A and 1B, and FIG. 3 shows a plan view ofthe main part of the thin film magnetic head.

[0054] An end surface of the return yoke layer 6, an end surface of thepole layer 11 and an end surface of the write shield layer 13 areexposed to the air bearing surface 20. In other words, the pole layer 11has an exposed surface 11M, and the return yoke layer 6 has an exposedsurface 6M. Herein, the exposed surface 11M corresponds to a specificexample of “a pole end surface” of the pole layer in the invention, andthe exposed surface 6M corresponds to a specific example of “an endsurface” of the return magnetic layer in the invention.

[0055] The pole layer 11 includes a front end portion 11A with a minuteuniform width W1 determining a recording track width on the hard diskand a rear end portion 11B coupled to the front end portion 11A in thisorder from a side closer to the air bearing surface 20. The rear endportion 11B has a width W2 which is larger than the width W1 of thefront end portion 11A (W2>W1) in a rear portion, and a graduallynarrowed width in a front portion.

[0056] The return yoke layer 6 has a substantially rectangular shapedstructure including a portion with a width continuously narrowed towardthe exposed surface 6M. More specifically, the return yoke layer 6includes, for example, a front portion 6A having two taper surfaces 6TRand 6TL on both sides to narrow the width of the front portion 6A fromthe both sides, and a rear portion 6B having a larger uniform width W3(W3>W2) than the width W2 of the rear end portion 11B of the pole layer11 in order from a side closer to the air bearing surface 20. A taperangle θ1 between each of the taper surfaces 6TR and 6TL in the frontportion 6A and the air bearing surface 20 is preferably within a rangeapproximately from 5° to 40°, and more preferably within a rangeapproximately from 10° to 30°. Herein, the front portion 6A of thereturn yoke layer 6 corresponds to a specific example of “a width changeportion” in the invention.

[0057] The write shield layer 13 has, for example, substantially thesame structure as the return yoke layer 6, and includes a front portion13A having two taper surfaces 13TR and 13TL on both side to narrow thewidth of the front portion 13A from the both sides, and a rear portion13B having the same width as the width W2 of the rear end portion 11B ofthe pole layer 11 in order from a side closer to the air bearing surface20. A taper angle θ2 between each of the taper surfaces 13TR and 13TL inthe front portion 13A and the air bearing surface 20 is, for example,equivalent to the taper angle θ1.

[0058] As a specific example of dimensions, for example, assuming thatthe width W3 of the return yoke layer 6 is approximately 88.0 μm, andthe width W2 of the write shield layer 13 is approximately 72.0 μm,

[0059] (1) in the case where the taper angles θ1 and θ2 areapproximately 5°, a width L1 and a length L2 of the taper surface 6TR(or 6TL) are approximately 2.0 μm and approximately 0.17 μm,respectively, and a width L3 and a length L4 of the taper surface 13TR(or 13TL) are approximately 2.0 μm and approximately 0.17 μm,respectively, and

[0060] (2) in the case where the taper angles θ1 and θ2 areapproximately 40°, the width L1 and the length L2 of the taper surface6TR (or 6TL) are approximately 2.0 μm and approximately 1.7 μm,respectively, and the width L3 and the length L4 of the taper surface13TR (or 13TL) are approximately 2.0 μm and approximately 1.7 μm,respectively.

[0061] Next, referring to FIG. 4, the structure of a hard disk on whichinformation is recorded by using the thin film magnetic head will bedescribed below. FIG. 4 is an illustration for describing the flow ofthe magnetic flux during recording by the thin film magnetic head, andshows the hard disk together with the thin film magnetic head.

[0062] A hard disk 200 in which a main part has a two-layer structure isfor perpendicular recording. The hard disk 200 comprises a back layer201 and a recording layer 202 laminated in this order on a base disk(not shown). The back layer 201 is provided mainly to form a guide pathfor a magnetic flux in the hard disk 200, and is made of, for example, asoft magnetic layer with high magnetic permeability. The recording layer202 is a layer on which information is recorded, and is made of amagnetic material on which information can be recorded by use ofmagnetization based upon a perpendicular magnetic field.

[0063] Next, referring to FIGS. 1A through 4, actions of the thin filmmagnetic head will be described below.

[0064] In the thin film magnetic head, in recording information, when acurrent flows into the thin film coil 8 of the recording head portion100B through an external circuit (not shown), a magnetic flux J1 isgenerated by the thin film coil 8. After the magnetic flux J1 generatedat this time is contained in the pole layer 11 through the yoke layer 9and is emitted from the exposed surface 11M of the pole layer 11 towardthe recording layer 202 of the hard disk 200, the magnetic flux J1 isreturned from the exposed surface 6M to the return yoke layer 6 throughthe back layer 201. At this time, the magnetic flux J1 emitted from thepole layer 11 generates a magnetic field (perpendicular magnetic field)for magnetizing the recording layer 202 in a direction perpendicular toa surface of the recording layer 202. Then, the perpendicular magneticfield magnetizes the recording layer 202 so as to record information onthe hard disk 200.

[0065] On the contrary, in reproducing, when a sense current flows intothe MR device 5 of the reproducing head portion 100A, the resistance ofthe MR device 5 is changed depending upon a signal magnetic field forreproducing which is generated from the recording layer 202 of the harddisk 200. A change in the resistance is detected as a change in thesense current so that the information recorded on the hard disk 200 isread out.

[0066] In the thin film magnetic head according to the embodiment, twotaper surfaces 6TR and 6TL are disposed on the both sides of the returnyoke layer 6, so because of the following reason, the occurrence oftrack erasing can be inhibited, and the reliability of magneticrecording can be improved.

[0067]FIG. 5 is an illustration for describing the flow of a magneticflux during recording by a conventional thin film magnetic head, andcorresponds to FIG. 4. FIG. 6 schematically shows results of measurementrelating to a correlation between the shape of the return yoke layer (inthe conventional thin film magnetic head having no taper surface, andthe thin film magnetic head according to the invention (the embodiment)having the taper surfaces) and magnetic field strength. In theconventional thin film magnetic head, for example, a return yoke layer106 has the same structure as that of the return yoke layer 6 in thethin film magnetic head according to the embodiment, except that thetaper surfaces 6TR and 6TL are not disposed on the return yoke layer106, and the return yoke layer 106 has a perfect rectangular shapehaving two corner portions 106CR and 106CL.

[0068] The conventional thin film magnetic head (refer to FIG. 5) canperform magnetic recording as in the case of the thin film magnetic headaccording to the embodiment. More specifically, during recordinginformation, a magnetic flux J2 emitted from the pole layer 11 isreturned to the return yoke layer 106 through the hard disk 200.However, in the thin film magnetic head, when the magnetic flux J2 isreturned to the return yoke layer 106, the returned magnetic flux J2 islocally concentrated on the corner portions 106CR and 106CL of thereturn yoke layer 106. Therefore, as shown in columns of “conventionalthin film magnetic head” in FIG. 6, the magnetic field strength islocally and pronouncedly increased in proximity to the corner portions106CR and 106CL. As a result, a perpendicular magnetic field isgenerated by not only the magnetic flux J2 emitted from the pole layer11 but also the returned magnetic flux J2 concentrated on the cornerportions 106CR and 106CL of the return yoke layer 106 without intention,so unnecessary recording is performed on the hard disk 200, therebyresulting in the occurrence of track erasing. Therefore, the reliabilityof magnetic recording decreases.

[0069] On the other hand, in the thin film magnetic head according tothe embodiment (refer to FIG. 4), the taper surfaces 6TR and 6TL aredisposed on the return yoke layer 6, and no corner portion which mayinduce concentration of the magnetic flux J1 is disposed on the returnyoke layer 6, so as shown in columns of “thin film magnetic head ofinvention” in FIG. 6, the magnetic filed strength is not locally andpronouncedly concentrated in proximity to the taper surfaces 6TR and 6TLof the return yoke layer 6. Therefore, in the embodiment, theconcentration of the returned magnetic flux J1 which causes a problem inthe conventional thin film magnetic head can be prevented, thereby, theprobability of the occurrence of unnecessary recording decreases, so theoccurrence of track erasing can be inhibited, and the reliability ofmagnetic recording can be improved.

[0070] Specifically, in the embodiment, the taper angle θ1 between eachof the taper surfaces 6TR and 6TL of the return yoke layer 6 and the airbearing surface 20 is preferably within a range of from 5° to 40°, andmore preferably within a range from 10° to 30°, so local concentrationof the returned magnetic flux which induces track erasing can beeffectively prevented. This is obvious from the result of an experimentshown in FIG. 7 and the following viewpoint. FIG. 7 shows a taper angledependence of a ratio of the magnetic field strength, and a “verticalaxis” indicates a ratio of a magnetic field strength when a magneticfield strength in proximity to the taper surface 6TR (θ1=0°) is 1, and a“lateral axis” indicates the taper angle θ1. Curves α and β in FIG. 7show changes in the ratio of the magnetic field strength incorresponding positions α and β shown in FIG. 3. As can be seen fromFIG. 7, the ratio of the magnetic filed strength in the position αpronouncedly decreases when the taper angle θ1 is approximately 2° orover. On the other hand, the ratio of the magnetic field strength in theposition β pronouncedly decreases when the taper angle θ1 isapproximately 45° or less. Accordingly, it is confirmed that when thetaper angle θ1 is within a range from 5° to 40°, an acceptable ratio ofthe magnetic field strength (approximately 0.3) is obtained, and morespecifically, when the taper angle θ1 is within a range of from 5° to30°, an adequate ratio of the magnetic field strength (approximately0.18) is obtained. However, when the processing accuracy of the minutetaper surfaces 6TR and 6TL disposed on the return yoke layer 6 isconsidered, the lower limit of the taper angle θ1 is preferably around10°0, so a practically adequate range of the taper angle θ1 is from 10°to 30°.

[0071] Moreover, in the embodiment, like the return yoke layer 6, twotaper surfaces 13TR and 13TL are disposed on the both sides of the writeshield layer 13, so in this point of view, the occurrence of trackerasing can be inhibited because of the following reason. As describedabove, unlike the return yoke layer 6, the write shield layer 13fundamentally has a function of magnetically shielding the pole layer 11from its surroundings, but the write shield layer 13 is made of the samemagnetic material as the return yoke layer 6, so during actualrecording, for example, as shown in FIG. 4, the magnetic flux J1 emittedfrom the pole layer 11 may be returned to not only the return yoke layer6 but also the write shield layer 13. In this case, when the writeshield layer 13 has a perfect rectangular shape and corner portions onboth sides thereof, local concentration of the magnetic flux J1 as inthe case of the return yoke layer 106 of the conventional thin filmmagnetic head shown in FIG. 5 occurs resulting from the existence of thecorner portions, so the possibility of the occurrence of track erasingincreases resulting from the concentration of the magnetic flux J1.However, in the embodiment, the write shield layer 13 has the tapersurfaces 13TR and 13TL, so the concentration of the magnetic flux J1 canbe prevented by the same effect as in the case where the return yokelayer 6 has the taper surfaces 6TR and 6TL, thereby, the occurrence oftrack erasing by the write shield layer 13 can be inhibited.

[0072] In the embodiment, in addition to the return yoke layer 6, thewrite shield layer 13 is tapered, but it is not necessarily limited tothis. As in the case of the write shield layer 13, any other part wherethe magnetic flux J1 may be returned during actual recording may betapered. More specifically, for example, as shown in FIG. 8, the bottomshield layer 3 is made of the same magnetic material as the write shieldlayer 13, so the magnetic flux J1 may be returned to the bottom shieldlayer 3. Therefore, the bottom shield layer 3 may be tapered to havetaper surfaces 3TR and 3TL on both sides. Also in this case, theconcentration of the magnetic flux J1 can be prevented by the sameeffect as in the case where the taper surfaces 13TR and 13TL aredisposed on the write shield layer 13, so the occurrence of trackerasing by the bottom shield layer 3 can be inhibited. Further, thestructure of a main part of the thin film magnetic head shown in FIG. 8is the same as in the case shown in FIG. 2, except for theabove-described characteristic part. Herein, the bottom shield layer 3having the taper surfaces 3TR and 3TL corresponds to a specific exampleof “a second shield layer” in the invention.

[0073] Moreover, in the embodiment, the return yoke layer 6 has flattaper surfaces 6TR and 6TL, but it is not necessarily limited to this.As long as the return yoke layer 6 has a continuously narrowed width inproximity to the air bearing surface 20, the structure of the returnyoke layer 6 can be freely modified. More specifically, for example, asshown in FIG. 9, the return yoke layer 6 may have curved surfaces 6KRand 6KL in positions corresponding to the taper surfaces 6TR and 6TL,respectively. Also in this case, the local concentration of the returnedmagnetic flux on the return yoke layer 6 can be prevented, so the sameeffect as that in the above embodiment can be obtained. The abovemodification relating to the structure of the return yoke layer 6 can beapplied to not only the return yoke layer 6 but also the write shieldlayer 13 (13KR and 13KL) or the bottom shield layer 3.

[0074] Further, in the embodiment, the return yoke layer 6 has afunction of returning the magnetic flux emitted from the pole layer 11and a function as a top shield layer which magnetically shields the MRdevice 5 from its surroundings, but it is not necessarily limited tothis. For example, in addition to the return yoke layer 6, the topshield layer is disposed, thereby the return yoke layer 6 mayindependently have a function of returning the magnetic flux, and thetop shield layer may independently have a function of magneticallyshielding. In this case, for example, a non-magnetic layer is preferablydisposed between the return yoke layer 6 and the top shield layer so asto prevent from propagating the magnetic flux between the layers.

[0075] Next, referring to FIGS. 1A through 3, and 10A through 16, amethod of manufacturing the thin film magnetic head according to theembodiment will be described below. FIGS. 10A and 10B through 13A and13B show sectional views of each step in the method of manufacturing thethin film magnetic head, and FIGS. 14 through 16 show plan views of themain part of the thin film magnetic head corresponding to each step inthe method of manufacturing the thin film magnetic head shown in FIGS.10A and 10B through 12A and 12B. The materials, thicknesses andstructural characteristics of parts of the thin film magnetic head havebeen already described above, and will not further described below.Mainly, a method of manufacturing the main part of the thin filmmagnetic head will be described in detail below.

[0076] The thin film magnetic head can be manufactured by use of, forexample, existing thin film processes including film formationtechniques such as plating, sputtering or the like, patterningtechniques using photolithography, etching or the like, and polishingtechniques such as machining, polishing or the like. More specifically,at first, as shown in FIGS. 10A and 10B, after the insulating layer 2 isformed on the substrate 1, the bottom shield layer 3 is selectivelyformed on the insulating layer 2 by use of, for example, frame platingso as to have a predetermined pattern shape. Frame plating will bedescribed in more detail below.

[0077] Next, as shown in FIGS. 10A and 10B, the shield gap film 4 isformed on the bottom shield layer 3 so as to bury the MR device 5.

[0078] Then, as shown in FIGS. 10A and 10B, a precursor return yokelayer 6Z is selectively formed on the shield gap film 4 by use of, forexample, frame plating. The precursor return yoke layer 6Z is apreparatory layer which becomes the return yoke layer 6 throughpolishing for forming the air bearing surface 20 in a later step.Hereinafter, a preparatory layer to be polished as in the case of theprecursor return yoke layer 6Z is called a “precursor” layer. When theprecursor return yoke layer 6Z is formed, for example, as shown in FIG.14, a rear portion 6ZC with a uniform width W3, a front portion 6ZA witha smaller uniform width than that of the rear portion 6ZC, and a middleportion 6ZB being disposed between the front portion 6ZA and the rearportion 6ZC and having two taper surfaces 6TR and 6TL so as tocontinuously narrow the width of the middle portion 6ZB toward the frontare included. At this time, the taper angle θ1 between each of the tapersurfaces 6TR and 6TL of the middle portion 6ZB and the air bearing 20(refer to FIG. 3; in this case, a surface including the X-axis and theZ-axis) which will be formed in a later step is preferably within arange approximately from 5° to 40°, and more preferably within a rangeapproximately from 10° to 30°. Herein, the precursor return yoke layer6Z corresponds to a specific example of “a precursor return magneticlayer” in the invention, and the middle portion 6ZB of the precursorreturn yoke layer 6Z corresponds to a specific example of “a precursorwidth change portion” in the invention.

[0079] Steps of forming the precursor return yoke layer 6Z by use offrame plating will be described in more detail below. At first, after anelectrode film (not shown) which becomes a seed layer for electroplatingis formed on the shield gap film 4, for example, a positive photoresistis applied to the electrode film to form a photoresist film. As thematerial of the electrode film, for example, the same material as thatof the precursor return yoke layer 6Z is used. Next, by use of a maskfor exposure having a patterned aperture corresponding to a plane shapeof the precursor return yoke layer 6Z, the photoresist film isselectively exposed through the patterned aperture, then an exposedregion of the photoresist film is developed so as to form a necessaryframe pattern for pattern plating. Next, a plating film is selectivelygrown by use of the frame pattern as a mask and the electrode filmformed in a previous step as a seed layer so as to selectively form theprecursor return yoke layer 6Z made of the plating film. Finally, afterthe frame pattern is removed, an unnecessary electrode film and anunnecessary plating film left in a region except for the precursorreturn yoke layer 6Z are selectively removed by use of, for example,etching so as to complete the steps of forming the precursor return yokelayer 6Z.

[0080] Next, the method of manufacturing the thin film magnetic headwill be described below.

[0081] After the precursor return yoke layer 6Z is formed, as shown inFIGS. 11A and 11B, the gap layer 7 (gap layer portions 7A, 7B and 7C)having the aperture 7K is formed on the precursor return yoke layer 6Zso as to bury the thin film coil 8, and the yoke layer 9 is formed so asto be magnetically coupled to the precursor return yoke layer 6Z throughthe aperture 7K. At this time, if necessary, the gap layer portion 7Cand the yoke layer 9 are polished so as to form the flat surface M.

[0082] Next, as shown in FIGS. 11A and 11B, the precursor pole layer 11Zis selectively formed on the flat surface M. For example, as shown inFIG. 15, the precursor pole layer 11Z is formed so as to include a frontportion 11ZA with the uniform width W1 corresponding to the front endportion 11A of the pole layer 11 which is finally formed and a rearportion 11ZB with a wider width corresponding to the rear end portion11B.

[0083] For example, steps of forming the precursor pole layer 11Z willbe described below. After a magnetic layer (not shown) made of thematerial of the precursor pole layer 11Z is formed, a mask layer forpatterning made of, for example, photoresist is formed on the magneticlayer. Then, the magnetic layer is patterned by using the mask layerthrough, for example, etching such as ion milling or the like so as toform the precursor pole layer 11Z in a pattern shape shown in FIG. 15.When the precursor pole layer 11Z is formed, for example, as shown inFIG. 11A, a region of the gap layer portion 7C on the periphery of thefront portion 11ZA is selectively dug down.

[0084] Next, as shown in FIGS. 12A and 12B, after the insulating layer12 is formed so that the precursor pole layer 11Z and its surrounding iscoated with the insulating layer 12, a precursor write shield layer 13Zis selectively formed on the insulating layer 12 through, for example,frame plating. For example, as shown in FIG. 16, the precursor writeshield layer 13Z is formed so as to include a rear portion 13ZC with theuniform width W2, a front portion 13ZA with a smaller uniform width thanthat of the rear portion 13ZC, and a middle portion 13ZB being disposedbetween the front portion 13ZA and the rear portion 13ZC and having twotaper surfaces 13TR and 13TL to continuously narrow the width of themiddle portion 13ZB toward the front. At this time, the taper angle θ2between each of the taper surfaces 13TR and 13TL of the middle portion13ZB and the air bearing surface 20 (refer to FIG. 3) which will beformed in a later step is preferably within a range approximately from5° to 40°, more preferably within a range approximately from 10° to 30°.

[0085] Next, as shown in FIGS. 13A and 13B, the overcoat layer 14 isformed so that the precursor write shield layer 13Z and its surroundingsare coated with the overcoat layer 14.

[0086] Finally, the whole formation including the precursor return yokelayer 6Z, the precursor pole layer 11Z and the precursor write shieldlayer 13Z is polished from the front through machining or polishing sothat a polished surface becomes flat, thereby as shown in FIGS. 1Athrough 3, the air bearing surface 20 is formed. When the air bearingsurface 20 is formed, the middle portion 6ZB of the precursor returnyoke layer 6Z, the front portion 11ZA of the precursor pole layer 11Zand the middle portion 13ZB of the precursor write shield layer 13Z arepolished until reaching a halfway point thereof. As a result ofpolishing, a region from the front portion 6ZA to the middle portion 6ZBin the precursor return yoke layer 6Z is selectively removed so as toform the return yoke layer 6 including the front portion 6A which hastwo taper surfaces 6TR and 6TL on the both sides to continuously narrowthe width of the front portion 6A toward the front and the rear portion6B magnetically coupled to the front portion 6A. Further, a region fromthe front portion 13ZA to the middle portion 13ZB in the precursor writeshield layer 13Z is selectively removed so as to form the write shieldlayer 13 including the front portion 13A which has two taper surfaces13TR and 13TL on the both sides to continuously narrow the width of thefront portion 13A toward the front and the rear portion 6B magneticallycoupled to the front portion 13A. Moreover, a part of the front portion11ZA of the precursor pole layer 11Z is selectively removed so as toform the pole layer 11 including the front end portion 11A with theuniform width W1 determining the recording track width and the rear endportion 11B magnetically coupled to the front end portion 11A. Thereby,the thin film magnetic head comprising the reproducing head portion 100Aand the recording head portion 100B is completed.

[0087] In the method of manufacturing the thin film magnetic headaccording to the embodiment, after the precursor return yoke layer 6Zincluding the middle portion 6ZB which has two taper surfaces 6TR and6TL to continuously narrow the width of the middle portion 6ZB towardthe front is formed, the precursor return yoke layer 6Z is polisheduntil reaching a halfway point of the middle portion 6ZB, so the returnyoke layer 6 having two taper surfaces 6TR and 6TL is formed. Therefore,the return yoke layer 6 can be formed with high accuracy, because of thefollowing reason.

[0088] As described above as the specific example of dimensions, thedimensions of two taper surfaces 6TR and 6TL are extremely minuterelative to the whole dimensions of the return yoke layer 6. Therefore,when the return yoke layer 6 is formed only in one step using, forexample, a pattern forming technique such as frame plating, it isdifficult to form the minute taper surfaces 6TR and 6TL with highaccuracy.

[0089] On the other hand, in the embodiment, the precursor return yokelayer 6Z is formed so that the middle portion 6ZB includes large tapersurfaces 6TR and 6TL in advance, and then the middle portion 6ZB of theprecursor return yoke layer 6Z is polished, so when the precursor returnyoke layer 6Z is polished, the width L1 or the length L2 of the tapersurfaces 6TR and 6TL can be freely controlled by adjusting an amount ofpolishing of the middle portion 6ZB. Therefore, in the embodiment,compared to the return yoke layer 6 formed only in one step using thepattern forming technique, the forming accuracy of the minute tapersurfaces 6TR and 6TL finally disposed on the return yoke layer 6 can besecured, so the return yoke layer 6 can be formed with high accuracy.

[0090] Moreover, in the embodiment, the precursor return yoke layer 6Zis polished by use of polishing for forming the air bearing surface 20,so another polishing is not required to polish the precursor return yokelayer 6Z. Therefore, in the embodiment, the precursor return yoke layer6Z is polished without increasing the number of manufacturing steps,thereby, the return yoke layer 6 having two taper surfaces 6TR and 6TLcan be formed. Therefore, the return yoke layer 6 can be formed moreeasily for a shorter time.

[0091] Moreover, in the embodiment, after the precursor write shieldlayer 13Z is formed so as to include the middle portion 13ZB having twotaper surfaces 13TR and 13TL to continuously narrow the width of themiddle portion 13ZB toward the front, the precursor write shield layer13Z is polished until reaching a halfway point of the middle portion13ZB so as to form the write shield layer 13 having two taper surfaces13TR and 13TL. Therefore, by the same effect as in the case where thereturn yoke layer 6 is formed, the forming accuracy of the minute tapersurfaces 13TR and 13TL can be secured, and the step of polishing to formthe air bearing surface 20 can be also used to form the write shieldlayer 13, so the write shield layer 13 can be formed more easily withhigher accuracy.

[0092] In the embodiment, the patterning technique using etching is usedto form the precursor pole layer 11Z, but it is not necessarily limitedto this. For example, frame plating may be used. However, in this case,it is difficult to form the uniform width W1 of the front portion 11ZAwith high accuracy, so, for example, the combined use of frame platingand etching is preferable. More specifically, after the precursor polelayer 11Z is formed so that the front portion 11ZA has a larger widththan the uniform width W1, the precursor pole layer 11Z is etched so asto form the uniform width W1 by narrowing the width of the front portion11ZA. Thereby, the precursor pole layer 11Z can be formed with higheraccuracy.

[0093] The present invention is described referring to the embodiments,but the invention is not limited to the embodiments, and can bevariously modified. For example, in the embodiment, the case where theinvention is applied to “a single-pole type head” is described, but itis not limited to this. For example, the invention may be applied to “aring-type head”.

[0094] Further, in the embodiments, the case where the invention isapplied to a composite thin film magnetic head is described, but it isnot limited to this. The invention is applicable to, for example, a thinfilm magnetic head for recording only comprising an inductive magnetictransducer for writing or a thin film magnetic head having an inductivemagnetic transducer for recording/reproducing. In addition, theinvention is applicable to a thin film magnetic head with a structure inwhich a device for writing and a device for reproducing are inverselylaminated. Further, the invention is applicable to not only theperpendicular recording system thin film magnetic head but also alongitudinal recording system (in-plane recording system) thin filmmagnetic head.

[0095] As described above, in the thin film magnetic head according tothe invention, the return magnetic layer is formed so as to include thewidth change portion with a width continuously narrowed toward an endsurface exposed to the recording-medium-facing surface, so the returnmagnetic layer has no sharp corner portion which can induce localconcentration of the returned magnetic flux in proximity to therecording-medium-facing surface. Therefore, the local concentration ofthe returned magnetic flux resulting from the existence of the cornerportion can be prevented, thereby the probability of the occurrence ofunnecessary recording decreases, so the occurrence of track erasing canbe inhibited, and the reliability of magnetic recording can be improved.

[0096] In the method of manufacturing the thin film magnetic headaccording to the invention, the precursor return magnetic layerincluding the precursor width change portion with a continuouslynarrowed width is formed, and then a laminate including the precursorreturn magnetic layer is polished until reaching a halfway point of theprecursor width change portion so as to form the recording-medium-facingsurface, thereby forming the return magnetic layer including the widthchange portion with a width continuously narrowed toward an end surfaceexposed to the recording-medium-facing surface. Therefore, compared tothe case where the return magnetic layer is formed only in one stepusing the pattern formation technique, the return magnetic layerincluding the width change portion can be formed with higher accuracyfor a shorter time.

[0097] Moreover, in thin film magnetic head according to the invention,an angle between each of the taper surfaces of the width change portionand the recording-medium-facing surface is within a range from 5° to40°, so the local concentration of the returned magnetic flux inproximity to the recording-medium-facing surface can be effectivelyprevented.

[0098] Further, in the thin film magnetic head according to theinvention, the first shield layer is formed so as to include a portionwith a width continuously narrowed from a predetermined position on aside away from the recording-medium-facing surface toward therecording-medium-facing surface, so even if the magnetic flux isreturned to the first shield layer during recording, the localconcentration of the returned magnetic flux in the first shield layercan be prevented. Therefore, the occurrence of track erasing by thefirst shield layer can be inhibited.

[0099] In addition, in the thin film magnetic head according to theinvention, the second shield layer is formed so as to include a portionwith a width continuously narrowed from a predetermined position on aside away from the recording-medium-facing surface toward therecording-medium-facing surface, so the local concentration of thereturned magnetic flux in the second shield layer can be prevented.Therefore, the occurrence of track erasing by the second shield layercan be inhibited.

[0100] Obviously many modifications and variations of the presentinvention are possible in the light of the above teachings. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A thin film magnetic head, comprising: a thinfilm coil generating a magnetic flux; a pole layer having a pole endsurface exposed to a recording-medium-facing surface facing a recordingmedium, and emitting the magnetic flux generated by the thin film coilfrom the pole end surface toward the recording medium; and a returnmagnetic layer where the magnetic flux emitted from the pole layer tomagnetize the recording medium is returned, wherein the return magneticlayer includes an end surface exposed to the recording-medium-facingsurface and a width change portion with a width continuously narrowedtoward the end surface.
 2. A thin film magnetic head according to claim1, wherein the width of the width change portion is narrowed from bothsides.
 3. A thin film magnetic head according to claim 2, wherein thewidth change portion has taper surfaces on both sides, and an anglebetween each of the taper surfaces and the recording-medium-facingsurface is within a range from 5° to 40°.
 4. A thin film magnetic headaccording to claim 1, further comprising: a first shield layermagnetically shielding the pole layer from its surroundings, wherein thefirst shield layer includes a portion with a width continuously narrowedfrom a predetermined position on a side away from therecording-medium-facing surface toward the recording-medium-facingsurface.
 5. A thin film magnetic head according to claim 1, furthercomprising: a magnetoresistive device; and a second shield layermagnetically shielding the magnetoresistive device from itssurroundings, wherein the second shield layer includes a portion with awidth continuously narrowed from a predetermined position on a side awayfrom the recording-medium-facing surface toward therecording-medium-facing surface.
 6. A thin film magnetic head accordingto claim 1, wherein the pole layer emits a magnetic flux for magnetizingthe recording medium in a direction perpendicular to a surface of therecording medium.
 7. A method of manufacturing a thin film magnetichead, the thin film magnetic head comprising a thin film coil generatinga magnetic flux, a pole layer having a pole end surface exposed to arecording-medium-facing surface facing a recording medium and emittingthe magnetic flux generated by the thin film coil from the pole endsurface toward the recording medium, and a return magnetic layer wherethe magnetic flux emitted from the pole layer to magnetize the recordingmedium is returned, the method comprising the steps of: forming aprecursor return magnetic layer as a preparatory layer of the returnmagnetic layer so as to include a precursor width change portion with acontinuously narrowed width; and polishing a laminate including theprecursor return magnetic layer until reaching a halfway point of theprecursor width change portion so as to form the recording-medium-facingsurface, thereby forming the return magnetic layer so as to have an endsurface exposed to the recording-medium-facing surface and include awidth change portion with a width continuously narrowed toward the endsurface.